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NTE842 Datasheet(PDF) 3 Page - NTE Electronics

Part No. NTE842
Description  Integrated Circuit Television Video IF Amplifier, Sync Separator, and AGC Processor
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Maker  NTE [NTE Electronics]
Homepage  http://www.nteinc.com
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NTE842 Datasheet(HTML) 3 Page - NTE Electronics

   
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Note 7. Retain tune voltage. With AGC bias open and video input switch closed, apply a 15mV(rms)
signal (as measured across an external 50
Ω termination) at 45.75MHz. As the AGC delay
current is varied from 0 to 1mA, the reverse tuner output voltage should go from high to low,
and forward tuner output from low to high.
Note 8. Same as Note 7, except increase input signal to 60mV(rms). As the delay current is varied
from 0 to 150
µA, the reverse tuner output voltage should go from high to low and forward
tuner output from low to high.
Note 9. The reverse tuner AGC output is an open collector. A 12K
Ω resistor may be connected to
a +12V supply or a 24K
Ω resistor to a +24V supply. The output high voltage will be within
1V of the supply voltage.
Note10. Apply a 45.75MHz, 50mV(rms) signal (as measured across an external 50
Ω termination) to
the fixture input. Apply a positive DC voltage to the AGC bias input and close the video input
switch. Adjust the AGC bias for a 2V reading at the video output. Measure the AC rms noise.
Note 11. Apply a 100 IRE bar–modulated IF signal to the fixture IF input. Modulation should be set
at 87.5%. Close the video input switch. Using an external 75
Ω to 50Ω matching pad and
50
Ω step attenuators, adjust the modulated IF signal to a 50mV equivalent (141.5mVp–p sig-
nal on a wide–band oscilloscope). Apply a key pulse to fixture input. Measure amplitude
of 100 IRE bar signal (black level to white level) at video output. (S + N)
÷ N = 20 Log10 (Bar
÷ Noise).
Note12. Signal conditions same as Note 11. Measure amplitude of sync output. Repeat test with IF
input attenuated 20dB (14.5mVp–p). Output at Pin12 is 9Vp–p to 12Vp–p.
Note13. A. Signal conditions same as Note 11. Measure amplitude of 100 IRE bar.
B. Repeat test with IF input attenuated 20dB. B% = 100 x Test 13B
÷ Test 13A.
C. Repeat test with IF input increased 6dB (283 mVp–p). C% = 100 x Test 13C ÷ Test 13A.
Note14. Same signal and conditions as Note 11. Measure ratio of 100 IRE bar signal to sync signal
of composite video output. Repeat test with input IF signal increased 6dB.
Note15. The sync tip to ground voltage is equivalent to the keyed AGC threshold. The test signal and
conditions are the same as Note 11. Measure the sync tip to ground voltage at the video
output.
Note16. A typical application circuit includes a tuner having at least 20dB AGC gain reduction.
2nd Amp Output
2nd Amp Input
1st Amp Input
1st Amp Output
Pin Connection Diagram
Sync Filter
Sync Output
Forward AGC Output
Input GND
1
2
3
4
Max Gain Bias
5
AGC Filter
6
Reverse AGC Output
7
16
15
14
13
AGC Delay
Substrate GND
12
11
(+) 12V Supply
10
Video Input
8
Key Pulse Input
9


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